Injection pump



W. HFELE Nov. 1, 1960 INJECTION PUMP INJECTION PUMP Walter Hfele,Fellbach, Germany, assignor to Robert Bosch G.m.b.I-1., Stuttgart,Germany Filed Aug. zo, 1956, ser. No. 604,869

Claims priority, application Germany Aug. 19, 1955 1 claim. (ci. 10a-41) The present invention relates to fuel injection equipment and moreparticularly to :a fuel injection pump for the selective operation of aninternal combustion engine with liquid fuel alone (diesel operation) orwith gas and a small quantity of liquid fuel as ignition fuel (dieselgas operation), and embodying two pump pistons one of which is adaptedto supply ignition fuel and has a smaller swept volume than the other.

It has been proposed that an individual pressure valve be associatedwith each of the two pump pistons. If it is intended to avoid, both withdisel operation and with diesel gas operation, subsequent dribbling froman associated injection nozzle and the attendant rapid carbonisation lofthe nozzle apertures, both pressure valves must be constructed so as torelieve the pressure in a pressure pipe line leading from the injectionpump to the injection nozzle at the end of the injection operation. Thisis almost essential, particularly when both pump pistons feed the sameinjection nozzle. In this case however the pressure valve associatedwith the smaller piston supplying the ignition fuel must also have thesame proportions as the pressure valve associated with the larger pistonsupplying the main fuel in the case of diesel operation.

According to the present invention in a fuel injection pump for theselective operation of an internal combustion engine with liquid fuelalone or with gas and a relatively small quantity of liquid ignitionfuel and embodying two pump pistons, one of said pistons is adapted tosupply the ignition fuel and has a smaller swept volume than the otherof said pistons which is adapted to supply the main fuel quantity whenworking Awith liquid fuel alone, both the pistons being adapted tosupply a common injection nozzle of the engine through a common pressurevalve and said one piston being adapted to control a supply passagethrough which fuel is displaced by said other piston to the pressurevalve.

The invention is further described by way of example with reference tothe accompanying drawings which illustrate one embodiment, and in which:

Fig. l shows a sectional View of the essential parts thereof adjustedfor diesel gas operation.

Fig. 2 is a section taken on the line II--ll of Fig. l to a largerscale, and

Fig. 3 is a section taken on the line III-HI of Fig. l with adjustmentfor diesel operation, also to a larger scale.

In a partly shown casing 1 of an injection pump is located a pumpcylinder 2 having a pump piston 3. On the upper face of the pumpcylinder 2 is coaxially mounted a second pump cylinder 4. A pin 5engaged in the two pump cylinders 2 and 4 provides relative angularlocation.

In the pump cylinder 4 slides a pump piston 6 which is coupled with thepump piston 3 by a T-head and slot connection so that it follows bothaxial and rotary displacement of the pump piston 3. A nipple 7 which isscrewed into the pump casing 1 provides pressure through a packing 8 topress the cylinder 4 against the cylinder 2 which is supported in thecasing 1.

tates Patint 0.,F

Patented Nov. Vl 1960 On the cylinder 4 is located a valve body 10having a displaceable valve member 11 which, in the closed positionshown, is pressed into its seat in the valve body by a compressionspring 12. In this position a cylindrical attachment 14 of the valvebody dips into its guide bore in the valve body 10. The spring 12 issupported against a coupling member 15 which is pressed against thevalve body 10 by a collar nut 16 screwed on the nipple 7; at the sametime the valve body is pressed against the pump cylinder 4. The couplingmember 1S has a pump outlet aperture 17 and is used for the connectionof a nonillustrated pressure pipe line leading to the correspondinginjection nozzle of the internal combustion engine which is also notshown.

In the casing 1 is an annular space 18 which surrounds the cylinder 2and communicates with a fuel inlet opening 19. The wall of the cylinder2 has transverse passages 20 and 21 which both communicate with theannular space and deiine inlet parts. The passage 21 is also used as areturn How passage. An axially directed passage 22 in the cylinder 4connects the working chamber 23 of the piston 3, by way of a transversebore 24, with the guide bore of the pump piston 6.

The pump piston 3 has a recess 27 which is partly limited by a helicalcontrol edge 26 and is permanently connected with the pump workingchamber 23 through an Iaxial groove 28. The pump piston 6 has a recess30 communicating through a radial bore 31 with an axial bore 33communicating with the working chamber 32. On the side opposite therecess 30 the pump piston 6 has a second recess 35 which extends fromthe crown thereof to the same axial level as the lower end of the recess30.

The transverse passage 21 enlarges into a groove at its endcommunicating with the annular space 18. A screw 38 located in the pumpcasing 1, projects by its shaft end into this groove and thus preventsthe pump cylinder 2 from twisting.

The drive of the pistons 3 and 6 is effected by a nonillustrated camagainst a non-illustrated return spring. The pistons 3 and 6 may beturned by a non-illustrated rack and pinion coupled to the piston 6whose movements are followed by the piston 3.

The pistons 3 and 6 of the injection pump are shown at bottomdead-centre and -in the angular position to which they :are adjustedwhen the engine is being operated with gas and with va small quantity ofliquid as ignition fuel, that is to say during `diesel lgas operation.The two pump working chambers 23 `and 32 have become fille-d with fuelfrom the annular space 18 through the passages 20, 21, and 22 during thepreceding suction stroke. In the angular position of the pistons shownin Fig. l and to which they have been adjusted by the aforementionedrack, the groove 28 of the pump piston 3 communicates permanently withthe return flow passage 21. Upon the pressure stroke all the fueldisplaced by the pump piston 3 is therefore returned to the annularspace 18 through the [groove 28 land the return ow passage 21. The fueldisplaced by the pump piston 6 is also urged into the annular chamber18, by way of the pump working chamber 23, until the opening of thepassage 24 into the bore of the cylinder 4 has been covered by thepiston 3 when the pressure in the working chamber 32 rises. Thisfdisplaces the valve member 11 to rise from its seat and, after theemergence of its attachment 14 from its guide bore, opens the passage tothe pump outlet opening 17 an-d therefor to the injection nozzle. Thepump piston- 6 then supplies fuel to the injection nozzle until itsrecess 30 uncovers the transverse bore 24 and thereby establishes aconnection between the working chamber 32 and the working chamber 23 andthe annular space 18 through the bores 33 and 31 and the passage 22. Atthis moment the injection operation, caused by the piston 6 alo-ne,terminates and the valve member 11 sinks, under the iniluence of thespring 12, back onto its seat. At the same time the pressure valve, lasa result of the entry of its cylindrical attachment 14 into its `guidebore,` increases the effective volume of the pressure pipe linedisposedl between the pressure valve and the injection nozzle therebyreducing the pressure in this pipe line to lavoid dribbling from theinjection nozzle. The fuel thus injected into a highly compressedgas/air mixture in the combustion chamber of the engine spontaneouslyignites and ignites the mixture.

When the engine is operated entirely with liquid fuel, that is with purediesel operation, the pump pistons 3 and 6 yare adjusted into theangular position shown in Figs. 2 and 3. In this position only the partof the recess 27 in the piston 3 which is limited by the inclinedcontrol edge 26 communicates with the return flow opening 21, whilst thegroove 28 no longer communicates with the transverse passage 21 as inthe angular piston position illustrate-d in Fig. l. The recess 35 of thepump piston 6 is now opposite the transverse bore 24. During thepressure stroke the pump piston 3 is therefore able, after the closingof the inlet passages 20 and 21, to supply fuel through the passage 22into the pump chamber 32 and through the opened pressure Valve 11 to theinjection nozzle until the inclined control edge 26 opens the returnflow passage 21. The pump piston 6 supplies the injection nozzle whenthe pistons are in this angular position, with the entire quantity offuel displaced by it after the operation of the piston 3 has commenced.

What is claimed as new and `desired to be secured by Letters Patent is:

In a fuel injection pump for operating an engine either with liquid fuelalone or with gas and a relatively small amount of liquid fuel, incombination, :a main cylinder having a working chamber at one endportion thereof, said main cylinder being formed with a rst passageleading from said working chamber to the exterior of said main cylinder;a housing carrying said main cylinder and formed with -a fuel supply andreturn chamber communicating with said first passage so that fuel ilo-wsto or from said `working chamber of said main cylinder through saidfirst passage thereof; an auxiliary cylinder co-axial with said maincylinder, having a smaller diameter than the same, and located ahead ofsaid working chamber thereof, said auxiliary cylinder having -a workingchamber at an end portion 4distant from said main cylinder; a passagemeans formed at least in part in said auxiliary cylinder and leadingvfrom said working chamber of said main cylinder to said working chamberof said auxiliary cylinder; a main piston in said main cylinder havingan `axial groove communicating with said rst pass-age in one angularposition of said main piston so that no fuel will be pumped byreciprocation of said main piston when it is in said one angularposition there of, said axial groove extending from the head end of saidmain piston `at said working chamber, and said main piston bein-g formedwith `an annular groove having a helical edge intersecting said axialgroove so that said main piston will pump Ia predetermined amount offuel depending upon the angle through which it is turned from said oneangular position; an auxiliary piston in said `auxiliary cylinderconnected to said main piston for axial and angular movement therewith,said auxiliary piston pumping liquid from said working chamber of saidauxiliary cylinder and said auxiliary piston yhaving an outer surfaceportion spaced from the inner surface of said auxiliary cylinder andangularly displaced from said passage means When said main piston is insaid one angular position thereof so that said auxiliary piston willduring its reciprocation close said passage means when said main pistonis in said one angular position thereof, said outer surface portion ofsaid auxiliary piston overlapping said passage means when said mainpiston is angularly displaced fromV said one angular position thereof,so that fuel pumped by said main piston will pass through said pass-agemeans to said working chamber of said auxiliary cylinder duringreciprocation of said auxiliary piston; and a single `discharge valvecommunicating with said Working chamber of said auxiliary cylinder fordischarging from the pump all fuel pumped by said pistons.

References Cited in the file of this patent UNITED STATES PATENTS833,457 Hammond Oct. 16, 1906 1,760,237 Iversen May 27, 1930 2,163,313Voit June 20, 1939 2,612,842 Steven et al. Oct.7, 1952 2,623,468 Stevenet al. Dec. 30, 1952 2,670,877 Logue Mar. 2, 1954 2,676,544 Schauer Apr.27, 1954 2,804,825 Mansfield et al. Sept. 3, 1957 FOREIGN PATENTS577,288 Germany May 29, 1933

